A. Feingold

Properties of titanium nitride thin films deposited by rapid‐thermal‐low‐pressure‐metalorganic‐chemical‐vapor‐deposition technique using tetrakis (dimethylamido) titanium precursor

Titanium nitride (TiNx) thin films were deposited onto InP by means of the rapid‐thermal‐low‐pressure‐chemical‐vapor‐deposition (RT‐LPMOCVD) technique, using the tetrakis (dimethylamido) titanium (Ti(NMe2)4 or DMATi) complex as the precursor. Depositions were successfully carried out at temperatures below 550 °C, pressure range of 5–20 Torr and duration of 50 to 90 s, to give layer thicknesses up to 200 nm and growth rates in the range of 0.8 to 4.5 nm/s. These films had a stoichiometric structure and contained nitrogen and titanium in a ratio close to unity, but also contained a significant amount of carbon and oxygen. The elements were spread uniformly through the films, the nitrogen was Ti bounded, and the carbon was partially titanium bonded and organic bonded as well. The film resistivity was in the range of 400–800 μΩ cm−2; the stress was always compressive, in the range of − 0.5 × 109 to − 2 × 1010 dyne cm−2, and the film had a good morphology. These layers performed as an ohmic contact while depos...

The influence of ammonia on rapid‐thermal low‐pressure metalorganic chemical vapor deposited TiNx films from tetrakis (dimethylamido) titanium precursor onto InP

The process kinetics, chemical composition, morphology, microstructures, and stress of rapid‐thermal low pressure metalorganic chemical vapor deposited (RT‐LPMOCVD) TiNx films on InP, using a combined reactive chemistry of ammonia (NH3) gas and tetrakis (dimethylamido) titanium (DMATi) liquid precursors, were studied. Enhanced deposition rates of 1–3 nm s−1 at total chamber pressures in the range of 3–10 Torr and temperatures of 300 °C–350 °C at a NH3:DMATi flow rate ratio of 1:8 to 1:15 were achieved. Stoichiometric film compositions were obtained, with carbon and oxygen impurity concentrations as low as 5%. Transmission electron microscopy analysis identified the deposited films as TiN with some epitaxial relationship to the underlying (001) InP substrate. This process provides a superior film to the preview RT‐LPMOCVD TiNx film deposited using only the DMATi precursor.

Rapid thermal low-pressure chemical vapor deposition of SiOx films onto InP

High quality SiOx films have been deposited onto InP substrates by means of a rapid thermal low‐pressure chemical vapor deposition technique, using oxygen (O2) and 2% diluted silane (SiH4) in argon (Ar) in the gas sources. Rapid deposition rates in the range of 15–40 nm s−1 with apparent activation energies of 0.12–0.15 eV were obtained at temperatures in the range of 350–550 °C, pressures between 5 and 15 Torr, and O2:SiH4 ratios in the range of 5:1–20:1. The SiOx films had refractive indexes between 1.44 and 1.50, densities of 2.25–2.37 g cm−3, internal compressive stresses of −0.5×109 to −3×109 dyn cm−2, and exhibited wet etch rates of 0.2–0.8 nm s−1 through the standard p‐etch process. The influence of the various process parameters on all the SiOx film parameters such as morphology and microstructure was examined.

W(Zn) selectively deposited and locally diffused ohmic contacts to p-InGaAs/InP formed by rapid thermal low pressure metalorganic chemical vapor deposition

Self‐aligned, locally diffused W(Zn) contacts to InGaAs/InP structures were fabricated by means of rapid thermal low pressure metalorganic chemical vapor deposition (RT‐LPMOCVD), using a reactive gas mixture that contained diethylzinc (DEZn), WF6, H2, and Ar. W(Zn) layers of about 30 nm thick were deposited at 500 °C for 20 s and at a total pressure of about 2 Torr, onto InGaAs and InP. Spontaneous formation of highly doped underlying InGaAs and InP layers about 150 nm thick with Zn concentration levels higher than 1×1018 cm−3 took place through the deposition of the W(Zn) layers. Post‐deposition, in situ annealing at temperatures of 500 °C or lower enhanced the indiffusion of Zn into the underlying semiconductor and reduced the specific resistance of the W(Zn)/InGaAs contact to a minimum value of 5×10−6 Ω cm−2.

Low resistance tungsten films on GaAs deposited by means of rapid thermal low pressure chemical vapor deposition

Low resistance tungsten (W) films were deposited onto GaAs substrates by means of rapid thermal low pressure chemical vapor deposition (RT‐LPCVD), using tungsten hexafluoride (WF6) gas reduced by hydrogen (H2). Deposition temperatures up to 550 °C for durations of up to 30 s were explored, resulting in deposition of relatively pure W films (containing less than 2% O2 and C). Post‐deposition sintering of the layers led to significant reduction of the resistivity to values as low as 50 μΩ cm. The efficiency of the deposition improved upon increasing the H2 flow rate up to 1250 sccm resulting in a deposition rate of about 10 nm/s at a total chamber pressure of 3.5 Torr and temperature of 500 °C. The films appeared to be polycrystalline with a very fine grain structure, regardless of the deposition temperature with good morphology and underwent a limited reaction with the underlying GaAs substrates.

Fast thermal kinetic growth of silicon dioxide films on InP by rapid thermal low-pressure chemical vapour deposition

Silicon dioxide films were deposited onto InP substrates in the ranges of 350-550 degrees C temperature, and 3-15 Torr pressure by means of the rapid thermal low-pressure chemical vapour deposition (RTLPCVD) technique. SiO2 films were deposited using a variety of Ox: SiH4 ratios in the range of 5:1-50:1, and deposition rates of 15-50 nm s-1. The high temperature and high rate deposition was obtained without creating any damage to the InP substrate surface, and resulted in highly densified SiO2 layers with good thickness control and low stress. The main parameters of the as-deposited and annealed films, such as deposition rate, density, refractive index, wet and dry etch rates, stresses, film microstructure, and the SiO2/InP interface quality are reported. These parameters were studied as a function of the process variables, which include deposition time, temperature, pressure, O2:SiH4 ratio, gas flow rates and chamber geometry.

Hybrid electron cyclotron resonance-RF plasma etching of TiNx thin films grown by low pressure rapid thermal metalorganic chemical vapour deposition

The use of F-based (SF6/O2, CF4/O2 and CHF3/O2) electron cyclotron resonance discharges for dry etching of TiNx films deposited onto InP by low pressure (3-10 Torr), rapid thermal metalorganic chemical vapour deposition is described. Etch rates of 50-100 AA min-1 are obtained for low DC biasing (-100 V) of the sample, giving rise to anisotropic features, infinite selectivity of etching TiNx over InP, and minimal damage to the semiconductor. SF6/O2 mixtures offer the fastest etch rates, while CHF3/O2 discharges produce significant polymer deposition under high pressure (20 mTorr) or high microwave power (>200 W) etching conditions.

Formation of TiNx ohmic contacts to InGaAs/InP by means of a load-locked integrated process

The authors have demonstrated the viability of forming an ohmic contact to InGaAs/InP structures by means of a load-locked integrated process. The wafer was loaded into a rapid-thermal low-pressure metallorganic chemical vapour deposition (RT-LPMOCVD) reactor and was exposed to a sequence of processes which led to the formation of an ohmic contact. After in situ cleaning of the wafer through a thermal cycle at 500 degrees C under a flow of tertiary-butylphosphine (TBP), which provided the free hydrogen needed for a mild etching of the surface, a layer of silicon oxide (SiOx) was deposited onto the InGaAs/InP via a rapid thermal cycle (500 degrees C, 30 s) in a low-pressure O2 and 2% diluted SiH4 chemical vapour deposition (CVD). Dry etching of 50 mu m wide contact windows was carried out using a contact stainless steel stencil mask, after unloading the wafer from the RT-LPMOCVD reactor chamber via the load-lock and loading it into an electron cyclotron resonance (ECR) dry etching chamber. In the final step the wafer was returned through the load-lock to the main chamber and a TiNx layer was selectively deposited into the via-holes and processed to provide an ohmic contact to the InGaAs/InP substrate. This work provides a solid demonstration of the feasibility of the single-wafer integrated process (SWIP) as an approach to replace the batch process traditionally used for InP-based optoelectronic devices.

Rapid thermal processing of WSix contacts to InP in low‐pressure N2:H2 and tertiarybutylphosphine ambients

WSix thin films deposited on InP substrates have been investigated for possible use as refractory ohmic contact materials for self‐aligned laser devices. The films have been rf diode sputtered using various Ar gas pressures from a single commercial target composed of W and Si with an atomic ratio of 1:1. Following the deposition, the WSix/InP samples were rapid thermal processed using a rapid thermal metalorganic chemical vapor deposition system in a controlled low‐pressure ambient of N2:H2 (9:1) and tertiarybutylphosphine. The as‐deposited films (∼100 nm thick) were amorphous but crystallized in the temperature range of 600–650 °C. The WSi2 phase forms first at 600 °C and then the W5Si3 nucleate with further heating at 650 °C. As a result of the crystallization, a reduction in the specific contact resistance to a value of 7.5×10−6 Ω cm2 and a decrease in the sheet resistance to values lower than 2 Ω/⧠ were observed. In addition, a significant reduction in the internal stress and an improvement in the WSi...

Growth of InP epitaxial layers by rapid thermal low pressure metalorganic chemical vapor deposition, using tertiarybutylphosphine

High‐quality InP layers with low impurity backgrounds have been grown by means of the rapid thermal low pressure metalorganic chemical vapor deposition technique, using tertiarybutylphosphine as the phosphorus source. The films were grown at a P:In ratio of 75 or higher, temperatures between 500 and 525 °C, a pressure of 2 Torr and growth rates as high as 2 nm/s. The undoped films were defect‐free with exhibited featureless morphologies, and minimum backscattering yields (Xmin) as low as 3.1%, measured by ion channeling. The electrical quality of the films (Nd=2.5×1016 cm−3, μ=4200 cm2/V s) was also excellent.